Almost non-invasive tests for the diagnosis for coronary artery disease have used visual estimates of percent stenosis from coronary angiograms as a gold standard for determining the sensitivity and specificity of diagnostic procedure. Physiologic studies of flow reserve have shown that visual estimates of percent stenosis are poor predictors of physiologic significance of the coronary obstruction. Because the gold standard of these non- invasive studies, percent stenosis, is now being called into very serious question the validation of these non-invasive imaging techniques must now be reconsidered. The aims of this study are to utilize a new methodology, direct measurements of flow reserve with intracoronary Doppler catheter and a potent coronary dilator papaverine as well as quantitative coronary angiography to reevaluate the sensitivity in the "threshold of positivity" of three cardiac non-invasive tests. The three cardiac non-invasive tests that will be examined are quantitative dipyridamole single photon emisision thallium scintigrams, computer based analysis of the exercise electrocardiogram and exercise abnormalities of left ventricular global and regional wall motion with radionuclide ventriculography. Completion of these studies should provide an improved understanding of the sensitivity of these commonly used diagnostic techniques for detecting physiologically significant coronary obstructive lesions.